Bis(2-fluoro-2,2-dinitroethoxy) 2,2,3,3,4,4,4-heptafluorobutoxymethane and a method of preparation

ABSTRACT

Bis(2-fluoro-2,2-dinitroethoxy) 2,2,3,3,4,4,4-heptafluorobutoxymethane,  (F), CF 3  CF 2  CF 2  CH 2  OCH[OCH 2  CF(NO 2 ) 2  ] 2 , is an energetic plasticizer with a melting point of -18° C. and thermal stability up to 150° C. HFBF is miscible with polyfluoro- and polynitropolymers and useful as a plasticizer in plastic-bonded explosives.

BACKGROUND OF THE INVENTION

This invention relates to plastic-bonded explosives and moreparticularly to energetic plasticizers for plastic-bonded explosives.

Examples of energetic plasticizers which are currently used inplastic-bonded explosives (PBXs) arebis(2-fluoro-2,2-dinitroethyl)formal (FEFO), butanetriol trinitrate(BTTN), and trimethylolethane trinitrate (TMETN). These compounds havevarious disadvantages which include limited thermal stability (BTTN,TMETN), high volatility (FEFO), toxicity (FEFO), and high melting point(FEFO). In addition, these energetic plasticizers are not miscible withfluoropolymers and can therefore not be used with these desirable newbinder materials for PBXs.

It would be desirable to provide a new high energy, thermally stableplasticizer which is also miscible with polyfluoro- andpolynitropolymers but with a lower melting point.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a new energeticplasticizer for plastic-bonded explosives.

Another object of this invention is to provide an energetic plasticizerhaving good thermal stability.

A further object of this invention is to provide an energeticplasticizer having a low melting point.

Still another object of this invention is to provide an energeticplasticizer that is miscible with fluoropolymers.

These and other objects of this invention are achieved by providing anew compound bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane and a method of preparing it.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention provides bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane (HFBF) which has been found toact as a general plasticizer for polyethylene glycol as well as variousnitro-containing prepolymers, and also for highly fluorinatedprepolymers such as the polyformal of2,4,4,5,5,6,6-heptafluoro-2-trifluoromethyl-3-oxa-1,7-heptanediol, HOCH₂CF₂ CF₂ OCF(CF₃)CH₂ OH. It is thermally stable up to 150° C. HFBF has adensity of 1.68 g/cm³ (22° C.) and its heat of formation is estimated tobe -594 kcal/mol, and the calculated detonation pressure is 228.9 kbar.HFBF has a very low melting point (-18° to -19° C.) compared with othernitroplasticizers of similar energy content such as FEFO (+14° C.) ortrifluoroethoxyFEFO (-1° to -3° C.). Its volatility is slightly lowerthan that of FEFO (0.0108 vs. 0.0167 mg/min at 117° C.). Thus HFBFexhibits a set of properties which is unmatched by any other energeticplasticizer of comparable energy content. In addition to being useful asa unitary plasticizer, HFBF may also be used in admixture with otherplasticizers to further improve and/or modify specific properties suchas energy content or melting point.

Bis(2-fluoro-2,2-dinitroethoxy) 2,2,3,3,4,4,4-heptafluorobutoxymethane,CF₃ CF₂ CF₂ CH₂ OCH[OCH₂ CF(NO₂)₂ ]₂, is prepared from2-fluoro-2,2-dinitroethanol, CF(NO₂)₂ CH₂ OH, and2,2,3,3,4,4,4-heptafluoro-1-butanol, CF₃ CF₂ CF₂ CH₂ OH, by thefollowing reaction sequence as illustrated in Examples 1, 2, and 3:##STR1##

Tris(2-fluoro-2,2-dinitroethoxy)methane, CH[OCH₂ CF(NO₂)₂ ]₃, is a priorart compound which is synthesized by reacting three moles of2-fluoro-2,2-dinitroethanol with one mole of chloroform by refluxing thereactants in the presence of ferric chloride as a catalyst. Theconditions of this reaction are illustrated by example 1 which isincorporated from U.S. Pat. No. 3,388,147, entitled"2-Fluoro-2,2-Dinitroethyl Carbonates and Production Thereof," which wasissued on June 11, 1968, to Mortimer J. Kamlet et al. (see col. 3,example III).

Next the tris(2-fluoro-2,2-dinitroethoxy)methane is refluxed withaluminum chloride and acetyl chloride to produce chlorobis(2-fluoro-2,2-dinitroethoxy)methane as illustated by example 2.

Finally, one mole of 2,2,3,3,4,4,4-heptafluoro-1-butanol is reractedwith each mole of chloro bis(2-fluoro-2,2-dinitroethoxy)methane toproduce the desired product bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxy)methane under conditions illustrated byexample 3. The choice of a solvent for this step is not critical. Anyinert solvent in which the reactants are soluble and which has asuitable boiling point may be used. Suitable solvents includedichloromethane, 1,1-dichloroethane 1,2-dichloroethane,1,1,2-trichloroethane, or mixtures thereof.

The general nature of the invention having been set forth, the followingexamples are presented as specific examples thereof. It will beunderstood that the invention is not limited to these specific examplesbut is susceptible to various modifications that will be recognized byone of ordinary skill in the art.

EXAMPLE 1 Prior Art Tris(2-fluoro-2,2-dinitroethoxy)methane [i.e.,tris(2-fluoro-2,2-dinitroethyl)orthoformate]

"A mixture of 0.5 g. anhydrous ferric chloride and 10 ml. chloroform wasplaced in a 30 ml. round-bottom flask fitted with a magnetic stirre anda reflux condenser connected through a bubbler to a methanol gas trap.2-fluoro-2,2-dinitroethanol, 2.0 g. (0.013 mole) was added and themixture stirred and refluxed for 24 hours, after which time the mixturewas collected [sic] to room temperature and the solvent removed invacuo.

"The residue was drowned in iced water, stirred until the ferricchloride dissolved and the crystalline product collected.Recrystallization of this material from chloroform-hexane gave 1.39 g.(68%) pure tris(2-fluoro-2,2-dinitroethyl)orthoformate (FDNEOF) as finecolorless needles, M.P. 110°-11.2°."

EXAMPLE 2 Chloro bis(2-fluoro-2,2-dinitroethoxy)methane

A solution of tris(2-fluoro-2,2-dinitroethoxy)methane (23.6 g, 0.050mol), aluminum chloride (12.0 g, 0.090 mol) and acetyl chloride (200 g)was refluxed for 1.5 hours and then concentrated on a rotary evaporatorto a viscous liquid. This was extracted with chloroform (2×50 ml). Aftertreatment with activated charcoal (2 g.), this solution was filtered andconcentrated (rot. evap., 40° C. bath) to 23 g. of residue from which8.53 g. (87%) of 2-fluoro-2,2-dinitroethyl acetate (bp 40°-3° C./0.1 mm)was removed by distillation. The residual liquid (14.14 g, 80% yield)was chloro bis(2-fluoro-2,2-dinitroethoxy)methane, free of contaminantsby ¹ H NMR analysis. Anal. Calcd for C₅ H₅ ClF₂ N₄ O₁₀ : C, 16.94; H1.42; Cl, 10.00; F, 10.72; N, 15.80. Found: C, 17.10; H, 1.78; Cl,10.08; F, 10.71; N, 15.42

EXAMPLE 3 Bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane(HFBF)

A solution of 9.26 g (0.026 mol) of the chlorobis(2-fluoro-2,2-dinitroethoxy)methane (Example 2), 6.00 g (0.030 mol)of 2,2,3,3,4,4,4-heptafluoro-1-butanol, and 20 ml of 1,2-dichloroethanewas refluxed for four hours. Volatiles were removed on a rotaryevaporator (40° C. bath) and the residue absorbed on 6 g of silica gel(Silica Gel 60, 70-230 mesh). The product mixture was separated on a 100g Silica Gel column with hexane/dichloromethane (4/1) to give 1.68 g. ofbis(2,2,3,3,4,4,4-heptafluorobutoxy) 2-fluoro-2,2-dinitroethoxymethaneand 11.57 g (86%) of bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane, (HFBF), mp -19° C. to -18° C.; ¹H NMR (CDCl₃) δ5.67 (s, 1), 4.79 (d, 4, J=16 Hz), 4.16 (t, 2, J=14 Hz).Anal. Calcd for C₉ H₇ F₉ N.sub. 4 O₁₁ : C, 20.86; H, 1.36; N, 10.81; F,33.01. Found: C, 20.88; H, 1.32; N, 10.68; F, 32.81.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. Bis(2-fluoro-2,2,-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane, CF₃ CF₂ CF₂ CH₂ OCH[OCH₂ CF(NO)₂]₂.
 2. A method of preparing bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane comprising the following steps inorder:(1) refluxing tris(2-fluoro-2,2-dinitroethoxy)methane withaluminum chloride and acetyl chloride to produce chlorobis(2-fluoro-2,2-dinitroethoxy)methane; (2) reacting one mole of2,2,3,3,4,4,4-heptafluoro-1-butanol with each mole of chlorobis(2-fluoro-2,2.-dinitroethoxy)methane to producebis(2-fluoro-2,2-dinitroethoxy) 2,2,3,3,4,4,4-heptafluorobutoxymethane;and (3) isolating the product bis(2-fluoro-2,2-dinitroethoxy)2,2,3,3,4,4,4-heptafluorobutoxymethane.
 3. The process of claim 2wherein the reaction in step (2) is run under reflux in a solventselected from the group consisting of dichloromethane,1,1-dichloroethane, 1,2-dichloroethane, 1,1,2-trichloroethane, andmixtures thereof.